Structure of nanoparticles from powder diffraction data using the pair distribution function

2005 ◽  
Vol 17 (5) ◽  
pp. S125-S134 ◽  
Author(s):  
Reinhard B Neder ◽  
Vladimir I Korsunskiy
Keyword(s):  
Distribution Function ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Pair Distribution Function ◽  
Powder Diffraction Data ◽  
Structure Of Nanoparticles

Effects of Bragg peak profiles and nanoparticle sizes on the real-space pair distribution function

2005 ◽  
Vol 38 (1) ◽  
pp. 55-61 ◽  
Author(s):  
Il-Kyoung Jeong ◽  
M. J. Graf ◽  
R. H. Heffner
Keyword(s):  
Distribution Function ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Pair Distribution Function ◽  
Bragg Peak ◽  
Real Space ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Bragg Peak Profiles ◽  
Peak Widths

A study of the effects of Bragg peak profiles and nanoparticle size broadening on the real-space pair distribution function (PDF) is presented, using `synthetic' powder diffraction data. Bragg peak profiles from both asymmetric time-of-flight (TOF) spallation neutron data and symmetric synchrotron X-ray data are considered. Due to their asymmetric peak profiles, the TOF data cause artificial shifts of the PDF peak positions towards higher pair distances. Coupled with this effect is a broadening of the PDF peak widths due to aQ-dependent spectrometer resolution, making reliable refinement of thermal parameters difficult. These effects become more pronounced as theQresolution becomes worse. By contrast, the symmetric X-ray powder diffraction data do not cause a systematic shift of the PDF peak positions, and the broadening of the PDF peak widths has a relatively minor effect on the extraction of the thermal parameters. Finally, nanoparticle size broadening of the asymmetric neutron TOF powder diffraction data causes a shift of the PDF peak positions towards lowerrvalues and smears the PDF intensities from one atomic shell to another.

FIDDLE. Simultaneous Indexing and Structure Solution from Powder Diffraction Data using a Genetic Algorithm and Correlation Functions

2019 ◽  
Author(s):  
Carmen Guguta ◽  
Jan M.M. Smits ◽  
Rene de Gelder
Keyword(s):  
Genetic Algorithm ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Correlation Functions ◽  
Cross Correlation ◽  
Simultaneous Optimization ◽  
Powder Diffraction Data ◽  
Structure Solution ◽  
Matching Technique

A method for the determination of crystal structures from powder diffraction data is presented that circumvents the difficulties associated with separate indexing. For the simultaneous optimization of the parameters that describe a crystal structure a genetic algorithm is used together with a pattern matching technique based on auto and cross correlation functions.<br>

Use of TALP with laboratory powder diffraction data from 2D detectors

2013 ◽  
Vol 28 (S2) ◽  
pp. S481-S490
Author(s):  
Oriol Vallcorba ◽  
Anna Crespi ◽  
Jordi Rius ◽  
Carles Miravitlles
Keyword(s):  
Organic Compounds ◽  
Structural Study ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Powder Pattern ◽  
Experimental Setup ◽  
Intensity Data ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Molecular Compounds

The viability of the direct-space strategy TALP (Vallcorba et al., 2012b) to solve crystal structures of molecular compounds from laboratory powder diffraction data is shown. The procedure exploits the accurate metric refined from a ‘Bragg-Brentano’ powder pattern to extract later the intensity data from a second ‘texture-free’ powder pattern with the DAJUST software (Vallcorba et al., 2012a). The experimental setup for collecting this second pattern consists of a circularly collimated X-ray beam and a 2D detector. The sample is placed between two thin Mylar® foils, which reduces or even eliminates preferred orientation. With the combination of the DAJUST and TALP software a preliminary but rigorous structural study of organic compounds can be carried out at the laboratory level. In addition, the time-consuming filling of capillaries with diameters thinner than 0.3mm is avoided.

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